The invention relates to a roughening tool for roughening a metallic surface of an inner walling or a pre-drilled workpiece core-bore and a method for roughening such a surface.
Such a roughening tool is used in vehicle construction for example for producing a cylinder head bore of a lightweight metal internal combustion engine made of aluminum or magnesium alloys. In order to increase wear resistance of the Al/Mg cylinder running surfaces of such an internal combustion engine a wear-resistant coating can be applied on the cylinder running surfaces in a thermal spray process.
For improving adhesiveness, the metal surface can be roughened with microscopic undercuts so as to form a roughened structure prior to applying the wear resistant coating. The roughening can for example be accomplished chemically or by laser treatment. As an alternative also a mechanical roughening can be used as it is known form DE 10 2009 006 694 A1 or from DE 10 2008 024 313 A1. In such a generic mechanical roughening process a roughening tool is used that has on the outer circumference a profiling contour with which a predefined roughened structure can be generated with the tool rotation by material removing or non material removing forming of the metallic surface. Thus in DE 10 2008 024 313 A1 the roughened structure is provided in two working steps, i.e., first in a first step in which undercuts are introduced into the metallic surface by material removal and/or embossing, and a second processing step in which the pre-forms are for example deformed by upsetting in a non-material removing process step.